Redox Control of Aluminum Ring-Opening Polymerization: A Combined Experimental and DFT Investigation

Abstract

The synthesis, characterization, and reactivity of an aluminum alkoxide complex supported by a ferrocene-based ligand, (thiolfan*)Al(OtBu) (1red, thiolfan* = 1,1′-di(2,4-di-tert-butyl-6-thiophenoxy)ferrocene), are reported. The homopolymers of l-lactide (LA), ε-caprolactone (CL), δ-valerolactone (VL), cyclohexene oxide (CHO), trimethylene carbonate (TMC), and their copolymers were obtained in a controlled manner by using redox reagents. Detailed DFT calculations and experimental studies were performed to investigate the mechanism. Mechanistic studies show that, after the insertion of the first monomer, the coordination effect of the carbonyl group, which has usually been ignored in previous reports, can significantly change the energy barrier of the propagation steps, thus playing an important role in polymerization and copolymerization processes.